Active battery cooling can be used to reduce thermal runaway risk and optimize battery performance and lifetime. Some active battery cooling systems blow air across the cells, or across a radiator that is thermally coupled to the cells. As another example, a battery cooling system can use cooling tubes and a liquid coolant to withdraw heat from the cells. Care must be taken to ensure that the liquid coolant does not short or otherwise electrically interfere with the batteries.
The loss of containment of coolant inside of a high voltage battery (either by system failure or abuse) can lead to an unsafe situation. When a battery is mounted in an electric or hybrid vehicle, the inherent risk of mechanical damage to the battery (e.g., in a vehicle crash) can pose an increased likelihood of unwanted leaks of liquid coolant. If the cooling system becomes punctured and liquid coolant spreads elsewhere in the battery, this can lead to significant adverse consequences for the battery and the entire vehicle.
For example, when directly exposed to conductive coolant or liquid, a high voltage battery can experience loss of isolation, high voltage shorting and arcing, and hydrogen generation. Any or all of these can ultimately lead to an explosion or fire. That is, internal electrical components of a high-voltage battery should be protected from immersion, splash, contact or spray, in case an internal cooling system fails or is damaged from fatigue, faulty components, or crash/abuse.
In the past, an electric fluid sensor has been used to detect leaked coolant. However, such a sensor does not itself remove any liquid from the battery pack. Upon or after leakage, a skilled technician can drain a battery pack of leaking coolant. However, this requires expert knowledge and some external indication of the leak.